1. Field of the Invention
The present invention relates to a retainer device for a heat sink assembly, and particularly to a retainer device incorporating a crank to readily and securely retain a heat sink on a central processing unit (CPU) of a computer.
2. Related Art
Heat sinks are often used to dissipate heat from CPUs of computers. Heat sinks can be attached to CPUs in a variety of ways, such as by gluing or using clips. An example of a conventional heat sink assembly is disclosed in Taiwan Patent Application No. 89210547. A clip of such heat sink assembly comprises a pressing portion, two spring portions extending from opposite ends of the pressing portion, and two locking arms depending from distal ends of the spring portions for engaging with a connecting member such as a socket. However, the clip and the connecting member are separate parts. Storage and transportation of these separate parts increases costs.
In addition, developments in integrated circuits have resulted in greater circuit density and complexity, thus increasing heat generated by operation of such integrated circuits within an electronic package such as a CPU. Therefore, bigger and heavier heat sinks are becoming increasingly necessary to efficiently remove the heat. Nowadays, strong resilient clips are often used to attach heat sinks onto electronic devices that incorporate a CPU. Accordingly, the force required to keep a heat sink in place has also increased. Unfortunately, in assembly, operators must exert great manual force when attaching the clip to the socket or to a motherboard. Extra tools are often required for installation or removal of the clip. There is considerable risk that during use of such tools, nearby components such as the motherboard will be accidentally damaged.
Another conventional heat sink assembly comprises a pair of symmetric clips to attach a heat sink to a CPU. The clips have to be attached to a retention module one after the other. Pressing forces applied to two sides of the heat sink are prone to be unequal. This can cause incomplete thermal contact between the heat sink and the CPU, thus reducing the heat dissipating efficiency of the heat sink assembly.
Thus a retainer device that can conveniently and safely secure a heat sink is desired. A copending application with Ser. No. 10/143,589 filed May 9, 2002, and with the same assignee, discloses an approach.
Accordingly, an object of the present invention is to provide a retainer device which can readily and securely attach a heat sink to a heat-generating electronic device such as a CPU.
Another object of the present invention is to provide a retainer device which does not require a tool when the retainer device is manipulated to attach a heat sink to a heat-generating electronic device such as a CPU, or when the retainer device is manipulated to detach the heat sink from the CPU.
A further object of the present invention is to provide a retainer device which applies equal pressing forces to a heat sink.
To achieve the above-mentioned objects, a retainer device for attaching a heat sink to a CPU comprises a retention module, a clamp, a U-shaped crank holder and a crank. The retention module has a rectangular base frame, and four posts extending upwardly from four corners of the base frame. The clamp has a pair of spaced hinge portions rotatably attached to two rear posts of the four posts. A hook depends from a front of the clamp. Two pivot rods extend outwardly from opposite ends of the crank holder, and are rotatably received in two corresponding vertical slots defined in two front posts of the four posts. The crank is substantially L-shaped, and comprises an offset pressing portion, two pivot arms extending from opposite ends of the pressing portion respectively, and an operation rod extending perpendicularly from one end of one of the pivot arms. The pivot arms are pivotably received in supporting arms of the crank holder, with the pressing portion being disposed between the supporting arms. When the operation rod is rotated toward the heat sink and locked in position, the pressing portion presses the hook of the clamp. The clamp accordingly pushes the heat sink toward the CPU, thereby causing the heat sink to intimately engage with the CPU. To release the heat sink from intimate engagement with the CPU, the operation rod is unlocked, whereupon the pressing portion of the crank is released from pressing engagement with the hook of the clamp.